Conventionally, since a polyolefin resin in general has many advantages such as having good productivity and being excellent in various kinds of moldability, as well as being lightweight, and having a corrosion resistance and an impact resistance, it has been widely used as for interiors and exteriors of automobiles or ships, household electric appliances or household furnishings, miscellaneous goods, and building materials. Such polyolefin-based resin molded product differs from a synthetic resin having a polarity, which is generally typified by a polyurethane resin, a polyamide resin, an acrylic resin, and a polyester resin, that the polyolefin resin is a non-polar and crystalline resin. Thus, with the generalized resin composition, it is extremely difficult to perform coating or adhering thereto.
Accordingly, when coating or adhering is performed on the polyolefin-based resin molded product, its surface has been activated with chromic acid, flame, corona discharge, plasma, or a solvent, such to enhance the adhesion to the surface. For example, for a bumper of automobiles, the surface is treated by etching with a halogen-based organic solvent such as trichloroethane, such to increase the adhesivity with a coated film, or a pretreatment such as a corona discharge treatment, a plasma treatment, and an ozone treatment is performed followed by carrying out the aimed coating or adhesion. In addition, the method of treating a surface of the substrate such as molded articles with a primer has chosen, and for example, there proposed a composition in which the polyolefin is introduced with maleic acid (Patent Document 1) or a composition in which chlorinated modified polyolefin is employed as a main component (Patent Document 2).
Metals such as a steel plate is also used in a wide range of fields such as interiors and exteriors for automobiles or ships, household electric appliances or household furnishings, miscellaneous goods, and building materials. The surface of a steel plate is coated for the main purposes of improving the appearance and giving an anti-corrosive property. In particular, it is important to prevent the cracks and abrasion of a coated film which are caused by a distortion due to an external force or an impact of materials. Currently, in order to prevent the problems, the thickness of a coated film is increased, or ones coated with a modified propylene-ethylene copolymer (Patent Document 3) obtained by graft copolymerizing maleic acid or anhydrides thereof are employed. However, since those include an organic solvent such as toluene and xylene, there has been a concern about the problems of safety and environment pollution. For such reason, there proposed a substance obtained by dispersing a composition, in which chlorinated modified polyolefin is employed as a main component, in water (Patent Document 4), and a substance obtained from an olefin polymer and a petroleum-based hydrocarbon resin (Patent Document 5).
However, since those substances employ a large amount of surfactant to be a water-based substance, problems arise in that the water resistance of a coated film and adhesivity to a substrate decrease and that the stickiness is generated due to its bleeding out to the surface. When the used amount of the surfactant which is the cause of above problems is reduced, problems arise in that the aqueous base cannot be formed or that the stability of an aqueous resin composition is poor. Further, there is a problem that the most of them cannot exhibit a sufficient adhesivity against a substrate.
Patent Document 1: Japanese Examined Patent Publication No. S62-21027
Patent Document 2: Japanese Examined Patent Publication No. S50-10916
Patent Document 3: Japanese Examined Patent Publication No. H06-057809
Patent Document 4: Japanese Unexamined Patent Publication No. H01-256556
Patent Document 5: Japanese Unexamined Patent Publication No. 2004-27055